[20151117]關于增量備份.txt
PORT_STRING VERSION BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
RMAN> backup incremental level 0 datafile 5 format '/home/oracle/backup/inc0_example_%u.dbf' TAG='INC0';
Starting backup at 2015-11-17 10:47:42
using channel ORA_DISK_1
channel ORA_DISK_1: starting incremental level 0 datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00005 name=/mnt/ramdisk/book/example01.dbf
channel ORA_DISK_1: starting piece 1 at 2015-11-17 10:47:42
channel ORA_DISK_1: finished piece 1 at 2015-11-17 10:47:43
piece handle=/home/oracle/backup/inc0_example_40qmfume.dbf tag=INC0 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 2015-11-17 10:47:43
--如果我改名删除這個增量備份呢？
$ mv inc0_example_40qmfume.dbf inc0_example_40qmfume.dbf_ORG
RMAN> backup incremental level 1 datafile 5 format '/home/oracle/backup/inc1_example_%u.dbf' TAG='INC1';
Starting backup at 2015-11-17 10:52:01
channel ORA_DISK_1: starting incremental level 1 datafile backup set
channel ORA_DISK_1: starting piece 1 at 2015-11-17 10:52:01
channel ORA_DISK_1: finished piece 1 at 2015-11-17 10:52:02
piece handle=/home/oracle/backup/inc1_example_43qmfuuh.dbf tag=INC1 comment=NONE
Finished backup at 2015-11-17 10:52:02
--增量1級備份成功。
RMAN> list backupset ;
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ -------------------
120 Incr 0 68.84M DISK 00:00:00 2015-11-17 10:47:42
BP Key: 120 Status: AVAILABLE Compressed: NO Tag: INC0
Piece Name: /home/oracle/backup/inc0_example_40qmfume.dbf
List of Datafiles in backup set 120
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- ------------------- ----
5 0 Incr 1774661 2015-11-16 16:16:33 /mnt/ramdisk/book/example01.dbf
122 Incr 1 32.00K DISK 00:00:00 2015-11-17 10:52:01
BP Key: 122 Status: AVAILABLE Compressed: NO Tag: INC1
Piece Name: /home/oracle/backup/inc1_example_43qmfuuh.dbf
List of Datafiles in backup set 122
5 1 Incr 1812018 2015-11-17 10:52:01 /mnt/ramdisk/book/example01.dbf
--說明備份并不是讀取增量備份檔案來比較的。而是通過控制檔案記錄的資訊來确定從那個scn開始。
SELECT recid
,file#
,incremental_level
,incremental_change#
,checkpoint_change#
,datafile_blocks
,blocks_read
FROM V$BACKUP_DATAFILE;
RECID FILE# INCREMENTAL_LEVEL INCREMENTAL_CHANGE# CHECKPOINT_CHANGE# DATAFILE_BLOCKS BLOCKS_READ
---------- ---------- ----------------- ------------------- ------------------ --------------- -----------
124 5 0 0 1774661 42240 39872
126 5 1 1774661 1812018 42240 42240
--可以從BLOCKS_READ看出，0級備份僅僅讀取使用的塊，而1級備份讀取全部的資料塊。要想充分使用增量備份最好打開塊跟蹤。
3.打開塊跟蹤檔案：
SCOTT@book> alter database enable block change tracking using file '/home/oracle/backup/change_tracking.dbf';
Database altered.
Starting backup at 2015-11-17 11:05:02
channel ORA_DISK_1: starting piece 1 at 2015-11-17 11:05:02
channel ORA_DISK_1: finished piece 1 at 2015-11-17 11:05:03
piece handle=/home/oracle/backup/inc1_example_44qmfvmu.dbf tag=INC1 comment=NONE
Finished backup at 2015-11-17 11:05:03
FROM V$BACKUP_DATAFILE
127 5 1 1812018 1812564 42240 42240
--再隻執行1次增量備份就可以看出效果了。
Starting backup at 2015-11-17 11:06:04
channel ORA_DISK_1: starting piece 1 at 2015-11-17 11:06:05
channel ORA_DISK_1: finished piece 1 at 2015-11-17 11:06:06
piece handle=/home/oracle/backup/inc1_example_45qmfvot.dbf tag=INC1 comment=NONE
Finished backup at 2015-11-17 11:06:06
RMAN>
SCOTT@book> /
128 5 1 1812564 1812604 42240 1
--最後一次讀取量明顯減少，這樣可以加快1級備份的速度。
SCOTT@book> alter database disable block change tracking ;
$ ll /home/oracle/backup/change_tracking.dbf
ls: /home/oracle/backup/change_tracking.dbf: No such file or directory
總結：
1.使用增量備份模式，最好打開塊跟蹤模式。加快1級備份以及累積備份的速度。
2.注意檢查0級備份是否完好，如果删除或者損壞，後果比較嚴重。
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